LCD panels have been widely used in electronic products, following the rapid development of optoelectronics technology and semiconductor technology. The advantages of the LCDs include high image quality, compact size, light weight, low driving voltage, and low power consumption. Thus LCDs have been applied in the manufacturing of products such as portable computers, personal digital assistants and color televisions, and are gradually replacing the cathode ray tubes (CRTs) used in conventional display devices. In short, LCDs are rapidly becoming a mainstream display apparatus.
A typical liquid crystal display includes an upper plate, a lower plate, and a liquid crystal layer sealed between the upper and lower plates. The liquid crystal layer is generally introduced between the upper and lower plates by a vacuum inhalation method, which is operated based on a capillary action principle and a pressure difference principle. The vacuum inhalation method includes the following steps: placing a sealed double-plate panel having an opening into a vacuum chamber, and evacuating the sealed panel via the opening; immersing the evacuated panel into a liquid crystal bath; and filling liquid crystal material into the sealed panel by means of the vacuum. However, performing the vacuum inhalation method is time-consuming. This is particularly the case for larger sized panels. If vacuum inhalation is performed too slowly, the yield rate is reduced and the production efficiency is unsatisfactory.
To overcome the abovementioned shortcoming, a one drop fill (ODF) method has been developed. First, a liquid crystal is dropped on a lower plate. The lower plate is then adhered to an upper plate. Compared with the conventional vacuum inhalation method, the ODF method requires a shorter working time, and the yield rate for manufacturing a LCD panel is relatively increased.
FIGS. 4 to 7 show various aspects of plate sealing with an adhesive when the ODF method is employed. FIG. 4 shows a lower plate provided with a plate sealing adhesive. FIG. 5 is an enlarged view of part of the plate sealing adhesive. FIG. 6 is a side viewed showing the same part of the plate sealing adhesive. A lower plate 10 is first provided. A plate sealing adhesive 30 is then applied to the lower plate 10. The plate sealing adhesive 30 runs from a first end 31 along edge portions of the lower plate 10 to a second opposite end 32. The two opposite ends 31, 32 of the plate sealing adhesive 30 are overlapped.
Referring to FIG. 7, after the lower plate 10 is filled with the liquid crystal material by way of the ODF method, an upper plate 20 is attached to the lower plate 10. The upper plate 20 is then pressed toward the lower plate 10 such that the upper plate 20 is adhered to the lower plate 10 to form a sealed panel having an opening. As a result, a joint portion 33 of the plate sealing adhesive 30 spreads toward an edge of the lower plate 10 and the upper plate 20, and toward an interior of the sealed panel. When this happens, elements contained within the sealed panel may be contaminated, and the display provided by the LCD panel may be impaired. If the plate sealing adhesive 30 spreads beyond the edges of the upper and lower plates 20, 10, the aesthetic appearance of the display device may be degraded.
In addition, the plate sealing adhesive 30 generally comprises a plurality of glass fibers. The glass fibers reinforce the cured plate sealing adhesive 30, so that the lower and upper plates 10, 20 are supported in a spaced apart configuration. However, when the lower and upper plates 10, 20 are pressed and adhered to each other, the glass fibers may cause the joint portion 33 spread unevenly. Therefore, the glass fibers may also contribute to impairment of the display of the LCD panel.
To avoid the spreading of the plate sealing adhesive, some alternative means have been developed. Referring to FIGS. 8 and 9, a plate sealing adhesive is arranged in a loop configuration on a lower plate. At a joint portion 43 of the plate sealing adhesive, portions of first and second ends 41, 42 of the plate sealing adhesive are overlapped, with a distal end of the second end 42 extending toward an edge of the lower plate.
FIG. 10 illustrates another configuration of a plate sealing adhesive. At a joint portion 53, a first end 51 and a second end 52 cross each other, and both ends 51, 52 extend obliquely toward an edge of a lower plate.
In the two above-described means, certain ends of the plate sealing adhesive extend toward the edge of the lower plate. Therefore spreading of the plate sealing adhesive into the inside of the LCD panel can be avoided. However, the two above-described means cannot completely avoid the spreading of the plate sealing adhesive. In addition, due to the existence of the overlapped portions 43, 53 of the plate sealing adhesive, it is difficult for the upper plate to be accurately disposed parallel with the lower plate when the upper plate is been attached to the lower plate. Furthermore, the extending and spreading portions of the plate sealing adhesive represent a waste of the plate sealing adhesive material.
What is needed, therefore, is a liquid crystal display panel which has an evenly distributed plate sealing adhesive and which is economically configured.